Question

The cell theory eventually replaced the concept of spontaneous generation as a result of what experimental evidence?

A) evidence that microorganisms can be filtered out with contaminated particles
B) evidence that microorganisms cannot grow in boiled broth if all the air is removed from a container
C) evidence that microorganisms cannot grow in boiled broth when new organisms were not allowed to enter
D) evidence that microorganisms can be killed when boiled out of broth

Answer 1

Louis Pasteur's swan-neck flask experiment provided evidence that microorganisms cannot grow in sterilized broth unless contamination occurs from new organisms entering, refuting the concept of spontaneous generation. So the correcct option is C.

Step-by-step explanation:

The cell theory eventually replaced the concept of spontaneous generation as a result of experimental evidence provided by Louis Pasteur. The correct answer to the question is C) evidence that microorganisms cannot grow in boiled broth when new organisms are not allowed to enter. Pasteur's swan-neck flask experiment was crucial to this discovery. He boiled broth within a flask with a swan-neck bend that allowed air to pass but prevented microorganisms from entering due to the curves. The broth remained sterile until the neck was broken, at which point contamination occurred. This demonstrated that microorganisms from the air, not a spontaneous generation, were responsible for microbial growth.

Pasteur, by using a unique design in his experiment, was able to show that when the broth is sterilized and no new microorganisms are allowed to enter, no microbial life develops. This conclusively refuted the idea of spontaneous generation and supported the germ theory of disease, suggesting that life only comes from pre-existing life. Pasteur's control group, with the flasks' necks intact, confirmed that without external contamination, the sterilized broth remained clear.

Answer 2

Answer:- Option C - evidence that microorganisms cannot grow in boiled broth when new organisms were not allowed to enter.

Explanation:-

• Theory of spontaneous generation stated that the living organisms can be created from non living matter. However, this theory was disapproved and replaced by the cell theory which stated that all living organisms are created from cells and new cells arise from pre-existing cells.

• There were several experiments conducted by various scientists to disapprove the theory of spontaneous generation however, the experiment that was most successful to do so was the one conducted by Louis Pasteur in 1859.

• Description of the experiment:-

-In his experiment, Pasteur boiled a meat broth in a flask (it was known that boiling the broth kills the micro organisms) and then heated the neck of the flask to bend into a S- shape.

The purpose of the S shaped neck was to allow the air to enter into the flask but not the micro-organisms as the micro organisms will settle by gravity in the neck and not reach into the flask.

observations of the experiment :-

1. Pasteur observed that even though the air entered the flask no micro organisms were growing in the flask.

2. Further,when he tilted the flask so that the broth came in contact with the part of the neck where the air borne microorganisms could have settled he was able to observe microbial growth in the flask.

These observations laid the theory of spontaneous generation to rest and proved that organisms can only grow in the presence of pre-existing cells which in this case were the microorganisms.